Savings & CD Calculator: APY Growth
Starting balance
Added every month (flexible mode only)
Annual percentage yield — interest as actually earned, compounding included
≈ 60 Months · 5 Years
Your projection
$19,319.07
- Total contributed
- $17,000.00
- Interest earned
- $2,319.07
- Monthly rate
- 0.327374%
Yearly breakdown
| Year | Balance | Contributed | Interest |
|---|---|---|---|
| 1 | $7,643.69 | $7,400.00 | $243.69 |
| 2 | $10,393.12 | $9,800.00 | $593.12 |
| 3 | $13,252.54 | $12,200.00 | $1,052.54 |
| 4 | $16,226.33 | $14,600.00 | $1,626.33 |
| 5 | $19,319.07 | $17,000.00 | $2,319.07 |
Savings & CD Calculator — APY Growth with Contributions
What does 4% really earn on $5,000 plus $200 a month? Enter the APY your bank quotes — the monthly rate is derived from it, so the yield you see is the yield you get — add contributions on top, and watch the future balance build with a contributions-vs-interest split. Flip to CD mode to lock a fixed term with no contributions and preset 3/6/12/60-month options.
Compare flexible savings against locked CDs, test what an extra $50 a month does over five years, and see the early-withdrawal estimate before you commit. Every calculation runs locally in your browser with no sign-up, and any scenario can be shared with a link.
The APY mechanics
APY already includes compounding, so the monthly rate is backed out of it rather than divided naively. The balance is the closed-form monthly-compounded future value of the deposit plus the annuity value of the contributions.
P = initial deposit · C = monthly contribution · n = number of months.
How it works
- Enter the APY — the yield as actually earned, compounding included.
- Add an initial deposit plus monthly contributions (flexible mode).
- Or flip to CD mode: contributions lock to 0, pick a preset term.
CD presets and the early-exit estimate
CD terms of 3, 6, 12 or 60 months are one tap away. Breaking early typically costs about 3 months of interest on the deposit — 10000 at 5% APY over 12 months grows to 10500.00, and an early exit costs ≈ 122.72.
What v1 leaves out
APY growth plus CD lock plus penalty estimate only — no tax treatment, no inflation, no tiered rates in v1. Follow-ups add real-dollar and ladder views.
Frequently asked questions
APY vs APR — what's the difference?
APR is the quoted rate before compounding; APY is what you actually earn with compounding included. This tool takes APY directly, so no conversion games.
When does a CD beat flexible savings?
When its APY is higher enough to offset the lock-in. Compare both modes above on identical inputs — the balances decide, not the labels.
How is the early-withdrawal penalty estimated?
As 3 months of interest on the initial deposit at the derived monthly rate. Real banks vary — treat it as an order-of-magnitude warning, not a quote.
When do contributions credit?
At the end of each month (ordinary annuity). Beginning-of-month contributions would earn slightly more; this tool uses the end-of-month convention.
How accurate is this calculator?
Exact to the cent against closed-form references: direct evaluation, no iterated rounding drift. Real accounts may compound daily rather than monthly — close, not identical.